Towards an understanding of coupled physical and biological processes in the cultivated Sahel – 2. Vegetation and carbon dynamics

Boulain, N.; Cappelaere, Bernard; Ramier, David; Issoufou, Hassane Bil-Assanou; Halilou, O.; Seghieri, Josiane; Guillemin, Françis; Oï, Monique; Gignoux, Jacques; Timouk, Franck

doi:10.1016/j.jhydrol.2008.11.045

Cited by 61 publications

(61 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…This was probably due to the differences between the soil evaporation rates, soil characteristics, deeps infiltration, and importance of the runoffs in relation with the vegetation types at the two sites. These results were in accordance with other findings reported between some sites more and less near each other in West Africa by other authors, especially concerning the rainfall regimes (Ago et al 2005;Boulain et al 2009;Seghieri et al 2009;Merbold et al 2009;Quansah et al 2015). It appears reasonable to consider both meteorological conditions at the two sites as similar overall.…”

Section: Micro-meteorological Conditionssupporting

confidence: 94%

“…This daily course suggests an influence of the VPD on the WUE, notably a partial stomatal closure impact besides the control by the radiation (Yang et al 2010). In Africa, similar daytime WUE courses were found for similar Sudano-Sahelian sites (Verhoef et al 1996;Moncrieff et al 1997;Friborg et al 1997;Boulain et al 2009;Ago et al 2014Ago et al , 2015. The two ecosystems were more efficient during morning and wet period than during afternoon and dry period.…”

Section: Sensitivity To Water Usagesupporting

confidence: 58%

“…The rainfall (weighing precipitation gauge, OTT; Hydrometry Ltd., Dublin, Ireland) was recorded at a height of 1.2 m. All these variables were sampled at 30 s time step and were averaged at half hour scale. The photosynthetic photon flux density (Q, μmol m −2 s −1 ) was estimated as twice the global radiation (R g , W m −2 ) (Scanlon and Albertson 2004;Boulain et al 2009;Ago et al 2014Ago et al , 2015. The CO 2 fluxes and meteorological conditions data were also available during 18 months, from 1st July 2008 to 31st December 2009.…”

Section: Climatic and Environmental Measurementsmentioning

confidence: 99%

“…For u * <0.1 m s −1 , the nighttime fluxes were rejected because they depended on the turbulence and led to an underestimation. For u * >0.1 m s −1 , the nighttime fluxes were stable and the threshold of 0.10 m s −1 was fixed for the two sites as per other authors for similar African sites (Archibald et al 2009;Boulain et al 2009;Merbold et al 2009;Ago et al 2014Ago et al , 2015.…”

Section: Data Treatment Analysis and Uncertainty Evaluationmentioning

confidence: 99%

“…At the field scale, it appears difficult to measure directly the photosynthesis and transpiration rates for the whole canopy or ecosystem (Baldocchi 1994). Therefore, the estimated WUE was defined in this study as the ratio of the absolute value of the net carbon uptake NEE and the net evapotranspiration E as used in other studies by several authors worldwide (Baldocchi et al 1985;Baldocchi 1994;Verhoef et al 1996;Moncrieff et al 1997;Scanlon and Albertson 2004;Boulain et al 2009;Keenan et al 2013;Ago et al 2014Ago et al , 2015. Especially, the WUE was used here for better understanding and comparison of the water status of the two contrasting ecosystems during the photosynthetic carbon uptake (Williams and Albertson 2004;Yang et al 2010;Medlyn and De Kauwe 2013).…”

Section: Data Treatment Analysis and Uncertainty Evaluationmentioning

confidence: 99%

See 4 more Smart Citations

Response of CO2 fluxes and productivity to water availability in two contrasting ecosystems in northern Benin (West Africa)

Ago

Agbossou

Cohard

et al. 2016

Annals of Forest Science

View full text Add to dashboard Cite

& Key message CO 2 fluxes were measured during 18 months in a forest and a savannah in northern Benin. Higher values of carbon fluxes were found during the wet season at each site. A strong dependency of carbon fluxes on water relations was found in two contrasting sites. The forest sequestered 640 ± 50 and the savannah 190 ± 40 g C m −2 year −1 . & Context In West Africa, the main mechanisms or factors governing the dynamics of ecosystems, especially the dynamics of the carbon fluxes and productivity, still remain less known. This study reports the carbon fluxes over two contrasting ecosystems, notably a protected forest (lat 9.79°N, long 1.72°E, alt 414 m) and a cultivated savannah (lat 9.74°N, long 1.60°E, alt 449 m) in northern Benin. The two sites were among those equipped by the AMMA-CATCH observatory and Ouémé 2025 project. & Aims Flux data were analyzed at the daily and seasonal scales in order to understand their controlling variables. We discussed the patterns of CO 2 fluxes and the characteristics of the two ecosystems. The study also focused on the different water usage strategies developed by the two ecosystems since the alternation between dry and wet seasons highly influenced the seasonal dynamics. Finally, the annual carbon sequestration was estimated together with its uncertainty. & Methods The carbon fluxes were measured during 18 months (July 2008-December 2009) by an eddy-covariance system over two contrasting sites in northern Benin. Fluxes data were computed following the standard procedure. The responses of CO 2 fluxes to the principal climatic and edaphic factors, and the canopy conductance were studied. & Results A clear CO 2 fluxes response to main environmental factors was observed, however with difference according to the seasons and vegetation types. The ecosystem respiration showed the highest values during the wet season and a progressive decrease from wet to dry periods. Also, the carbon uptake values were high during the wet period, but Handling Editor: Erwin DreyerContribution of the co-authors Expédit Evariste Ago conducted mainly the data analysis and prepared the manuscript with contributions from all co-authors. The field work with the eddy-covariance technique was carried out by Jean-Martial Cohard and Sylvie Galle who processed the raw data of fluxes. Marc Aubinet and Euloge Kossi Agbossou assisted in the data analyses. All authors read and approved the final manuscript which was submitted. low during the dry period. However, the CO 2 fluxes for the protected forest were always higher than that for the cultivated savannah within each defined period. This was due to the seasonal changes not only in phenology and physiology but also to the acclimation to environmental conditions, especially to the soil water availability. The water use efficiency was influenced by VPD during the day conditions for two ecosystems. However, the VPD response curve of water usage was relatively constant for the protected forest during the transitional and wet seasons. In contrary, for t...

show abstract

Section: Micro-meteorological Conditionssupporting

confidence: 94%

Section: Sensitivity To Water Usagesupporting

confidence: 58%

Section: Climatic and Environmental Measurementsmentioning

confidence: 99%

Section: Data Treatment Analysis and Uncertainty Evaluationmentioning

confidence: 99%

Section: Data Treatment Analysis and Uncertainty Evaluationmentioning

confidence: 99%

See 3 more Smart Citations

Response of CO2 fluxes and productivity to water availability in two contrasting ecosystems in northern Benin (West Africa)

Ago

Agbossou

Cohard

et al. 2016

Annals of Forest Science

View full text Add to dashboard Cite

show abstract

The Surface Energy Budget Computed at the Grid‐Scale of a Climate Model Challenged by Station Data in West Africa

Diallo

Hourdin

Rio

et al. 2017

J Adv Model Earth Syst

View full text Add to dashboard Cite

In most state‐of‐the‐art climate models, systematic errors persist in the representation of the rainfall seasonality, near surface air temperature, and surface energy budget over West Africa, even during the dry season. Most biases are related to an incorrect latitudinal position of the monsoon structures. To disentangle the role of the large‐scale dynamics from that of the physical processes in these biases, simulations are performed with the LMDZ general circulation model in which the horizontal winds are nudged toward reanalysis. Wind nudging greatly improves the position of the ITCZ as well as the representation of the components of the surface energy budget directly impacted by the water budget and hence facilitates a more systematic analysis of remaining biases associated with the physics in the model. The great potential of wind nudging to compare the energetics of the atmospheric column in climate models at grid cell scale with station observations, even for coarse grid models, is then shown. Despite the improved water advection and rainfall seasonality in the nudged simulations, errors consisting in a cold bias during the dry season over Sahel, an underestimated seasonal variation of surface albedo, and an overestimation of the solar incoming flux remain. The origin of these remaining biases is further investigated by conducting a series of dedicated sensitivity experiments. Results highlight the key role of the soil thermal inertia, the turbulent mixing efficiency, the surface albedo, and the aerosols and clouds radiative effects in the representation of meteorological 2m‐variables and surface energy budget.

show abstract

AMMA's contribution to the evolution of prediction and decision‐making systems for West Africa

Polcher¹,

Parker

Gaye

et al. 2011

Atmospheric Science Letters

View full text Add to dashboard Cite

The AMMA (African Monsoon Multidisciplinary Analysis) project set out to better understand the geophysical processes which govern the evolution of the monsoon and provide the science needed to improve prediction and decision-support systems. The control exerted by weather and climate on agronomic production, water resources and public health was studied to evaluate the potential for populations to adapt. AMMA made advances which have the potential to improve forecasts from weather to climate scales. Translating them into operational tools for decision making will require improvements to the observational networks, and stronger support for the organizations which generate and disseminate application forecasts.

show abstract

Towards an understanding of coupled physical and biological processes in the cultivated Sahel – 2. Vegetation and carbon dynamics

Cited by 61 publications

References 34 publications

Response of CO2 fluxes and productivity to water availability in two contrasting ecosystems in northern Benin (West Africa)

Response of CO2 fluxes and productivity to water availability in two contrasting ecosystems in northern Benin (West Africa)

The Surface Energy Budget Computed at the Grid‐Scale of a Climate Model Challenged by Station Data in West Africa

AMMA's contribution to the evolution of prediction and decision‐making systems for West Africa

Contact Info

Product

Resources

About